Silver oxide cell and its manufacture

Abstract

A silver oxide cell which comprises a positive electrode comprising a shaped body of silver oxide as a main positive active material, a negative electrode and an alkaline electrolyte, characterized in that the shaped body is a molded product of a composition comprising particles of silver oxide and particles of manganese dioxide, both particles having a certain particle size distribution, so that a detectable voltage difference is produced prior to complete consumption of the discharge capacity of the cell, whereby the termination of the discharge capacity of the cell can be anticipated.

What is claimed is: 
     
       1. A primary silver oxide cell which comprises a positive electrode comprising a shaped body of silver oxide as a positive active material, a negative electrode comprising a negative active material and an alkaline electrolyte, characterized in that the shaped body is a molded product of a composition comprising particles of silver oxide and particles of manganese dioxide, the particle size distribution of both of said particles being not less than 90% of particles of not more than 10μ in particle size and not less than 60% of particles of not more than 5μ in particle size, and said shaped body having a packing density of not less than 4.5 g/cm 3 , whereby a detectable voltage difference is produced prior to complete consumption of the discharge capacity of the cell. 
     
     
       2. The silver oxide cell according to claim 1, wherein the main positive active material is silver(I) oxide or silver(II) oxide, or mixture thereof. 
     
     
       3. The silver oxide cell according to claim 1, wherein the negative active material is zinc. 
     
     
       4. The silver oxide cell according to claim 1, wherein the content of manganese dioxide is not more than 20% by weight based on the weight of the shaped body. 
     
     
       5. The silver oxide cell according to claim 4, wherein the content of manganese dioxide is not less than 1% by weight based on the weight of the shaped body. 
     
     
       6. The silver oxide cell according to claim 5, wherein the content of manganese dioxide is from 3 to 17% by weight based on the weight of the shaped body. 
     
     
       7. The silver oxide cell according to claim 1, wherein the weight proportion of the silver oxide, the manganese dioxide and zinc as the negative active material is controlled to satisfy the following two inequalities:   [Zn].sub.min >[Ag.O].sub.max       [Zn].sub.max <[Ag.O+MnO.sub.2 ].sub.min     wherein [Zn] min  is a minimum value in the variation of the discharge capacity of the zinc, [Zn] max  is a maximum value in the variation of the discharge capacity of the zinc, [Ag.O] max  is a maximum value in the variation of the discharge capacity of the silver oxide and [Ag.O+MnO 2  ] min  is a minimum value in the variation of the total discharge capacity of the silver oxide and the manganese dioxide.